JPH06351106A - Converter controller - Google Patents

Abstract

PURPOSE:To effectively reduce a harmonic wave of a specific frequency by providing a carrier frequency setter for setting an arbitrary carrier frequency and a carrier phase setter for arbitrarily setting a phase of a carrier in a converter control circuit for each of a plurality of PWM converters. CONSTITUTION:A carrier frequency fc is set by a carrier frequency setter 34 of each converter control circuit 30, and phases Q1-Q4 of each carrier are set by a carrier phase setter 35. As a result, each carrier generator 36 generates a carrier of the set frequency fc which is deviated by a set phase Q from a power source frequency input from a synchronous power source 11, and inputs it to a comparator 33. The comparator 33 compares the carrier with a modulated wave Vs', and outputs a converter switching pulse signal which is turned ON only by a time in which the carrier exceeds the wave Vs' to switching elements of allotted converters CONV1-CONV4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a converter control device for performing switching control of a PWM converter for converting an AC power source fed from an AC overhead wire into a DC voltage having a predetermined voltage.

[0002]

2. Description of the Related Art Conventionally, a main circuit used to drive an induction motor for electric railway has a structure shown in FIG.
That is, the power of the AC overhead wire is supplied from the pantograph 1 and supplied to the converter 3 via the transformer 2. Then, the converter 3 performs AC / DC conversion and the rectified DC power is smoothed by the filter capacitor 4,
Further, the induction motor 6 is driven by re-converting it into desired AC power by the inverter 5 which converts DC / AC. Then, usually, the transformer 2 is provided with a plurality of secondary windings, a plurality of main circuits 7 as described above are connected, and the induction motors are operated in parallel.

In such a main circuit configuration, a PWM modulation method is generally used as a control method for each converter 3, but conventionally, the frequency of the carrier wave in the PWM modulation is the power supply frequency for feeding. Had chosen an odd multiple of. Further, the phase of the carrier wave of the PWM modulation is selected to be a different value among a plurality of converters to reduce the ripple on the primary side of the transformer 2 and the harmonics in a specific frequency region.

A typical example of how to determine the combination of the frequency and phase of the carrier wave of the converter by this conventional converter control device is as follows. The frequency of the carrier wave is mainly related to the capability of the power semiconductor element that constitutes the converter, and in order to suppress the heat generation due to the switching loss, it is selected to be the lowest frequency allowable in terms of ripple, and then,
The carrier phase was chosen to reduce harmonics in a particular frequency band, such as the band used for the signal.

[0005]

However, in such a conventional converter control device, an attempt to reduce a certain specific harmonic causes an increase in the harmonic in another region, which is not necessarily the frequency of the carrier wave. There was a problem that the phase could not be selected optimally.

For example, the case where four converters are operated in parallel will be described as an example. The harmonic distribution when one converter is PWM-modulated by the carrier wave fc Hertz is as shown in FIG. 2 times the frequency fc of the carrier wave, 4
Harmonics remarkably appear around the double and 8-fold frequencies 2fc, 4fc and 8fc.

Therefore, when the harmonics are reduced by parallel operation of the two converters and the harmonics in the vicinity of 0 fc are to be eliminated, the carrier phase of the two converters is 90 °. To shift the harmonics in the vicinity of 0 fc, shift the carrier phase of the two converters by 45 °. To eliminate the harmonics in the vicinity of 8 fc, remove the two harmonics. The purpose is achieved by shifting the phase of the converter carrier by 22.5 °.

If four converters are used,
Two of the harmonics in the vicinity of 2fc, 4fc, and 8fc can be selected and eliminated. Therefore, in the case of operating four converters in parallel, the configuration of two + two,
The two units are each shifted by 90 °, and the other units are 22.5
The configuration is such that the PWM carrier wave generator 10 for each converter 4 shifts 0 °, 22.5 ° as shown in FIG.
A carrier wave having a phase relationship of °, 90 °, 112.5 ° is generated, and PWM modulation of each converter 4 is performed by this. Reference numeral 11 is a synchronous power source.

However, in the converter control device having such a configuration, the harmonic distribution as shown in FIG.
Although the harmonics in the vicinity of c can be extinguished, the higher harmonics in the vicinity of 4fc are supposed to remain.

Therefore, in order to eliminate even the harmonics of 4 fc, the number of secondary windings of the transformer 2 and the number of converters may be set to 8, but when divided in this way,
There are problems that the winding structure of the transformer becomes complicated and difficult, and that the weight and volume of the device increase remarkably.

The present invention has been made in view of such conventional problems, and provides a converter control device capable of arbitrarily setting the frequency and phase of a carrier wave in order to reduce a desired harmonic. With the goal.

[0012]

According to a first aspect of the present invention, there is provided a transformer for transforming a voltage fed from an AC overhead wire, a plurality of PWM converters connected to a secondary side of the transformer, and a PWM of the plurality of PWM converters. In a converter control device including a converter control circuit that performs control, a carrier frequency setter that sets an arbitrary carrier frequency and a carrier phase that arbitrarily sets the phase of a carrier in a converter control circuit for each of a plurality of PWM converters And a setting device.

According to a second aspect of the invention, in the converter control device of the first aspect, when the number of PWM converters is n,
The carrier frequency setting device sets the carrier frequency to 1 / n of the frequency of a specific harmonic, and the carrier phase setting device sets the carrier phase to π (180 °) / n.

[0014]

In the converter control device according to the first and second aspects of the invention, in the converter control circuit for each converter, the carrier frequency is set by the carrier frequency setting device and the carrier phase is arbitrarily set by the carrier phase setting device. It is possible to set a frequency and a phase for a carrier wave that can effectively cancel a specific harmonic wave, and effectively suppress the harmonic wave.

Further, in the converter control device of the present invention, when the number of PWM converters is n, the carrier frequency setter sets the carrier frequency to 1 / n of the frequency of a specific harmonic.
The carrier wave phase setter sets the phase of the carrier wave to π (18
0 °) / n. For example, when four converters are connected in parallel, a carrier frequency fc that is ¼ times the harmonic to be reduced is set for each converter control circuit. , 0 °, 9 between each converter control circuit
By selecting the phase difference of the carrier wave so that it becomes 0 °, 45 °, 135 ° and operating each converter in phase difference, 2f
It becomes possible to effectively cancel the higher harmonics of c and 4fc.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows, as an embodiment of the present invention, a configuration of a converter control circuit 30 for each converter 3 in the converter control device having the four converters 3 shown in FIG. 3 in parallel. Each converter control circuit 30 performs proportional integral compensation calculation on the deviation between the current set value Is * and the actual current output Is of the converter 3,
A proportional-integral compensator 31 that outputs a voltage control amount ΔV, an adder 32 that compensates the actual voltage Vs of the converter 3 with the voltage control amount ΔV, and outputs a modulated wave signal Vs *, and this adder 32.
The comparator 33 is provided with one input of the modulated wave Vs * given by

Each converter control circuit 30 also has a carrier frequency setter 34 for arbitrarily setting the carrier frequency fc.
And a carrier wave phase setter 35 for arbitrarily setting the carrier wave phase
And the carrier frequency fc set by these carrier frequency setters 34 and connected to these setters 34, 35 in order to generate the carrier wave at the phase θ set by the carrier wave phase setter 35. A carrier wave generator 36 is also connected to the synchronous power supply 11 for synchronizing with the power supply frequency, and the carrier wave generated by the carrier wave generator 36 is supplied to the other input of the comparator 33. Therefore, the comparator 33 outputs the modulated wave Vs *.
Is compared with the carrier wave from the carrier wave generator 36 to output the converter gate pulse signal of each converter 4.

Next, the operation of the converter control device having the above configuration will be described.

As shown in FIG. 3, the converter control device of this embodiment has CONV1, C for one transformer 2.
Four converters 3 of ONV2, CONV3 and CONV4 are connected in parallel.

In each converter control circuit 30, if the carrier frequency fc is set in the carrier frequency setting device 34 and the phase θ of each carrier is set in the carrier phase setting device 35, the synchronous power supply 11 is set in the carrier generator 36.
The carrier wave of the set frequency fc is generated by shifting the set phase with respect to the power supply frequency input from the.

On the other hand, in the converter control circuit 30, the input current Is of the converter 3 which is in charge of its own circuit is taken in by the current detector, and the proportional-integral compensator 32 takes the current command value I.
The voltage control amount ΔV is calculated according to the deviation between s * and the actual current,
This is added to the actual voltage Vs in the adder 32 to perform voltage correction, and the voltage command obtained by this voltage correction is given to the comparator 33 as the modulated wave Vs *.

The comparator 33 compares the modulated wave Vs * with the carrier wave and outputs the converter switching pulse signal which is turned on only during the time when the carrier wave exceeds the modulated wave Vs *, to the switching element of the converter 3 which is in charge of the converter switching pulse signal.
Each converter 3 receives P by this switching pulse signal.
DC power by WM modulation will be output.

Therefore, in the converter control device provided with four converters 3, each converter control circuit 3
The carrier frequency fc is set by the carrier frequency setter 34 of 0.
Is set to a frequency that is ¼ times the specific harmonic to be reduced.

Further, the phase difference of the carrier waves of each converter 3 is determined by the converter control circuit 30 of each converter 3.
By the carrier phase setting device 35 of θ1 = 0 °, θ2 =
90 °, θ3 = 45 °, and θ4 = 135 ° are set.

When the carrier frequency fc and its phase difference are set in this way and the four converters 3 are operated in phase difference, the harmonic distribution of the current flowing through the primary winding side of the transformer 2 results as shown in FIG. Becomes

When this harmonic distribution is compared with the harmonic distribution shown in FIG. 4 which is observed when one converter is operated, the peaks of 2fc and 4fc among the harmonics are canceled out and only 8fc remains. Has become. However, since the carrier frequency fc is selected to be 1/4 of the frequency of the specific harmonic to be reduced, the peak of the harmonic does not appear in the vicinity of the frequency 4fc of the desired harmonic, and the specific frequency is reduced. This means that the harmonics of can be effectively canceled out.

The present invention is not limited to the above embodiment, and when two converters are operated in parallel, the carrier frequency fc is selected to be 1/2 of the specific harmonic frequency to be reduced, By selecting the phase difference between 0 ° and 90 ° and performing the phase difference operation, it is possible to cancel the peak of the harmonic between 2fc, and the peak of the harmonic is generated near the harmonic 2fc of the specific frequency that was desired to be reduced. It does not appear, and it becomes possible to effectively cancel the harmonic of the specific frequency. Further, in the case of operating one converter, by selecting the carrier frequency to be the same as the specific harmonic frequency to be reduced, the harmonic of the specific frequency can be canceled.

Therefore, in general, when there are n PWM converters, the carrier frequency setting unit sets the carrier frequency to 1 / n of the frequency of a specific harmonic, and the carrier phase setting unit sets the carrier phase to π ( 180 °) / n, for example, when four converters are connected in parallel, a carrier frequency fc that is ¼ times the harmonic to be reduced for each converter control circuit is set. Set 0 °, 90 °, 45 between each converter control circuit
2fc, 4fc by selecting the phase difference of the carrier wave so that
It becomes possible to effectively cancel the harmonics of.

Further, although the switching element of the converter is not particularly limited in the above embodiment, the converter control device of the present invention particularly uses the IGBT (insulated gate transistor) as the switching element, and the frequency that the converter can take. It is advantageous to apply to the control of a high withstand voltage, large current type converter that enables a high frequency range.

[0031]

As described above, according to the invention of claim 1,
In the converter control circuit for each converter, the carrier frequency is set by the carrier frequency setting device and the carrier phase is set arbitrarily by the carrier phase setting device. An optimal combination can be selected according to the frequency of the harmonic wave whose phase is desired to be reduced, and the harmonic wave of a specific frequency can be effectively reduced.

According to the second aspect of the present invention, when there are n PWM converters, the carrier frequency setting unit sets the carrier frequency to 1 / n of the frequency of a specific harmonic, and the carrier phase setting unit sets the carrier frequency. Since the phase is set to π (180 °) / n, it is possible to effectively cancel up to the harmonic of the frequency of n times the carrier wave.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a harmonic distribution characteristic according to the above embodiment.

FIG. 3 is a block diagram showing a main circuit configuration of four general converters.

FIG. 4 is an explanatory diagram showing a harmonic distribution characteristic generated when one converter is in operation.

FIG. 5 is a block diagram of a conventional example.

FIG. 6 is an explanatory view showing a harmonic distribution characteristic of a conventional example.

[Explanation of symbols]

 1 Pantograph 2 Transformer 3 Converter 7 Main circuit 11 Synchronous power supply 30 Converter control circuit 33 Comparator 34 Carrier frequency setting device 35 Carrier phase setting device 36 Carrier generator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiko Ujiie No. 1 Toshiba-cho, Fuchu-shi, Tokyo Toshiba Corporation Fuchu factory

Claims (2)

[Claims] 1. A transformer for transforming a voltage fed from an AC overhead wire, and a plurality of P's connected to a secondary side of the transformer.
WM converter and PW of the plurality of PWM converters
A converter control device comprising an M control converter control circuit, wherein a converter control circuit for each of the plurality of PWM converters and a carrier frequency setter for setting an arbitrary carrier frequency are arbitrarily set. And a carrier wave phase setting device. 2. The converter control device according to claim 1, wherein when there are n PWM converters, the carrier frequency setting unit sets the carrier frequency to 1 / n of a frequency of a specific harmonic, A converter controller, wherein a phase setter sets the phase of a carrier wave to π (180 °) / n.